The present technology relates to materials and implants useful in maintaining patency in a passageway, such as an airway, and treating conditions where a passageway in a human or other animal subject has collapsed or weakened like in tracheomalacia or a tracheoesophageal fistula. Tracheomalacia or tracheobronchomalacia (TBM) are congenital or acquired deficiencies of tracheal and/or bronchial cartilages. These conditions may be characterized by flaccidity of the supporting tracheal or bronchial cartilage, resulting in airway obstruction, respiratory difficulties and, in severe cases, death. It is estimated that this condition affects about 1 in 2,100 children. TBM presents with respiratory difficulties, chronic cough, wheezing, recurrent infections, and in severe cases, acute life-threatening events. In adults and infants who have severe forms of TBM that are unresponsive to medical management or have life-threatening symptoms, surgical intervention may be necessary. Severe cases can result in death or require tracheostomy with ventilation for 2-3 years, a burden on the child and family. Current treatment techniques often include mechanical ventilation, implantation of tracheal stems and surgery. For example, as noted in the Cochrane reviews, outcomes of all surgical/mechanical interventions to date have been widely associated with failure, morbidity and mortality.
Surgical/mechanical devices for addressing TBM can be broadly categorized into stents, namely devices placed inside or within the passageway (e.g., trachea), and splints, namely devices implanted externally around the passageway (e.g., the trachea). Stents offer an easier surgical approach, but are associated with more complications, including stent migration, granulation tissue leading to secondary obstruction, the need for multiple procedures and even death. Further, conventional silicone and metal tracheal stents have posed difficulties in placement, stent migration or distortion, lack of tissue growth, permanence and decreased adjustability. These complications have prompted the U.S. Food and Drug Administration (FDA) to issue a warning against the use of tracheal stents.
Splints, however, have also exhibited various complications, including tracheal erosion and granuloma formation. These detrimental effects are believed to be attributable to the conventional materials used to form the splints in that they are too stiff. Further, there is concern that overly stiff devices restrict tracheobronchial growth, causing more long term complications, especially in children. Tracheal banding in rat models has been found not only to restrict tracheal growth, but to lead to smaller overall lung volumes, less alveoli and smaller overall body growth. However, devices that are not stiff enough fail to create/maintain tracheobronchial patency and, further, easily migrate from the desired position. While degradable devices have been proposed as a partial solution, these devices have been observed to degrade too rapidly, thus allowing insufficient time for the trachea to remodel and become structurally competent, thereby failing to resolve the TBM or other passageway defects. Thus, implantable devices that improve upon these issues to decrease mortality, improve patient outcomes, including improve growth to permit the defective passageway to develop structural competency, and to enhance the quality of life of an animal having such a passageway defect would be desirable.